Shower Mixer and Non-return Valves

[rob99]

I've just had fitted a shower mixer which incorporates a Non-Return valve (NRV). Unfortunately, the recommended pressure reducing valve was not fitted. My DHW is an unvented system so the shower mixer has about 5 bar on the HW side and 6.5 bar on the CW. That is outside the manufacturers stated operating pressure.

My question is; when the pressure reducing valve is fitted will the NRV then operate correctly or will it have been damaged by the high pressure and need replacing?

Thanks for any help.

 

[Chalked]

Your hot water should be restricted to 3 bar! All balanced cold supplies should have also being taken from this.

 

[townfanjon]

Something wrong here .... Please tell me your unvented has a pressure reducing valve fitted, you shouldnt be getting 5 bar on hot

 

[Ermintrude]

About..... He's probably measured static with a bike pump!

 

[rob99]

Yes, there is a PRV fitted on the hot side.

 

[townfanjon]

Rob is prv fitted before the cylinder (where it should be)

 

[rob99]

Yes; Pressure Reducing Valve reducing the pressure of cold water supply to hot water tank.
Also, a pressure relief valve on the HW tank to ensure it is not over-pressured.

My belief is that at the shower mixer the CW is overcoming the NRV and causing the over-pressure on the HW side which in turn causes the Pressure Relief Valve to operate as it should. My theory is that because pressure reducing valve was not fitted to the supply to the mixer it is outside the manufacturer's stated parameters and there not acting effectively as a non-return.

Any thoughts?